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Questions and Answers
Which ketone body is mainly volatilized in the lungs?
Which ketone body is mainly volatilized in the lungs?
Which enzyme plays a critical role in regulating the entry of fatty acids into the oxidative pathway?
Which enzyme plays a critical role in regulating the entry of fatty acids into the oxidative pathway?
What happens to CPT-I activity and lipolysis in a well carbohydrate-fed state?
What happens to CPT-I activity and lipolysis in a well carbohydrate-fed state?
Which condition is NOT directly associated with ketosis?
Which condition is NOT directly associated with ketosis?
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What is the primary consequence of prolonged ketosis?
What is the primary consequence of prolonged ketosis?
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In the context of diabetes mellitus, what primarily causes excess lipolysis?
In the context of diabetes mellitus, what primarily causes excess lipolysis?
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What happens to excess acetyl-CoA during ketogenesis?
What happens to excess acetyl-CoA during ketogenesis?
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How does CPT-I activity change during starvation or a low carbohydrate diet?
How does CPT-I activity change during starvation or a low carbohydrate diet?
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Study Notes
Ketonemia
- Ketonemia is the presence of excess ketone bodies in the blood.
- It is usually caused by increased production of ketone bodies by the liver rather than reduced utilization by extrahepatic tissues.
Ketone Bodies
- Acetoacetate and 3-hydroxybutyrate can be readily reformed into acetyl-CoA.
- Acetone is difficult to reform into acetyl-CoA and is largely volatilized in the lungs.
Regulation of Ketogenesis
- Ketogenesis is mainly regulated by nutritional status.
- After uptake of free fatty acids by the liver, they can be:
- β-oxidized to form acetyl-CoA that enters the citric acid cycle, with excess acetyl-CoA forming ketone bodies.
- Esterified to form triacylglycerol and phospholipid.
Carnitine Palmitoyltransferase-I (CPT-I)
- CPT-I regulates the entry of fatty acids into the oxidative pathway.
- CPT-I activity is affected by nutritional status:
- In a well-carbohydrate-fed state:
- CPT-I activity is low.
- Lipolysis is decreased.
- β-oxidation and ketogenesis are depressed.
- Most fatty acids are esterified to form triacylglycerol and phospholipid.
- In starvation or a low-carbohydrate diet:
- CPT-I activity is high.
- Lipolysis is increased.
- β-oxidation is increased.
- More acetyl-CoA is converted to ketone bodies.
- In a well-carbohydrate-fed state:
Clinical Aspects of Ketogenesis
- Ketoacidosis results from prolonged ketosis.
- Higher-than-normal quantities of ketone bodies in the blood and/or urine constitute ketonemia (hyperketonemia) and/or ketonuria, respectively.
- Ketosis occurs in:
- Starvation.
- Pathologic states, such as:
- Diabetes mellitus due to:
- Reduced glucose utilization for energy production.
- Excess lipolysis due to the absence or defect of insulin.
- Hypoglycemia due to:
- Reduced glucose concentration available for energy production.
- Excess lipolysis due to the reduction of insulin.
- Diabetes mellitus due to:
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Description
This quiz covers the concept of ketonemia, the presence of excess ketone bodies in the blood, and the regulation of ketogenesis, including the role of nutritional status.
